The present invention relates to surgical instruments and, more specifically, to a disposable electrosurgical pencil capable of selectively providing cut or coagulate waveforms to a scalpel electrode mounted on the pencil.
Various devices have been developed and disclosed to exploit the reaction of living tissue to an applied electrical current. High current applied over a relatively small area of tissue can provide rapid and localized transformations. For instance, many systems have been developed to apply radio frequency current through a thin scalpel electrode, which is collected and returned via a second electrode applied over a wide area of tissue remote from the surgical site. These systems generally provide two modes of operation: cut, which is analogous to the function of the traditional knife scalpel, and coagulate, which produces hemostasis.
In a typical surgical procedure utilizing electrosurgical techniques, a physician may desire to alternate the mode of operation of the electrosurgical apparatus. In order to minimize the severity of surgical trauma and the risk of infection and other complications, it is always important to minimize the time and attention taken away from the patient to control surgical instruments of any complexity, including electrosurgical systems. To this end, a variety of electrosurgical scalpel electrode handles, known as electrosurgical pencils, have been developed utilizing control switches so that the surgeon may alternate modes without removing his or her eyes, hands, or attention from the patient.
U.S. Pat. No. 4,170,234 discloses an electrosurgical pencil with a rocker switch for selection of mode of operation. As is typical among such devices, the pencil is connected to an electrosurgical generating apparatus by a cable comprising three conductors: a first signal line, a second signal line, and a common line which serves not only to return the selected control signal to the generator, but also to deliver current to the scalpel electrode. Thus, all three conductors are maintained at high voltage, with the control signal conductors differing in voltage slightly from the common conductor so that a relatively small current will serve to select the mode of operation desired. The rocker switch maintains constant contact through spring contacts with the common conductor. The spring contacts also serve to support the fulcrum of the rocker switch within the housing of the pencil. The two control signal conductors and the common conductor lie in a plane below the rocker switch, and the metallic bottom surface of the rocker switch is shaped so as to contact with one or the other of the signal conductors on either side of the common conductor when the appropriate end of the rocker switch is depressed. Among the disadvantages inherent in the disclosed pencil is the lack of a moisture-proof seal around the rocker switch, and the lack of a fixed fulcrum for the rocker switch. The floating fulcrum allows either end of the switch to be jammed beneath the surface of the pencil casing, thereby delivering current to the scalpel electrode when the surgeon may believe it to be inoperative.
U.S. Pat. No. 4,112,950 discloses another electrosurgical pencil utilizing a three-conductor current control and delivery circuit. Two push-button switches rest atop a conductor and pivot around an internal fulcrum defined by posts and a casing extension. The common conductor and the control signal conductors are connected to posts beneath the conductor. When a button is depressed, it contacts and connects a common conductor post to a signal conductor post. It is evident that both buttons could be depressed simultaneously, because they share no rigid common body to prevent such an occurrence. Moreover, this system like the previous system lacks a moisture-proof seal around the switch contacts as well as a jam-proof switch due, again, to the use of an internal fulcrum.
Another electrosurgical pencil is disclosed in U.S. Pat. No. 4,034,761. This device is also devoid of a moisture-proof seal around its rocker switch, and is provided with an internal fulcrum for the switch which may allow jamming within the casing of the pencil. Moreover, this device also permits pressure to be exerted on both ends of the rocker switch simultaneously to make contact between all three conductors, thereby creating a potentially dangerous electrical circuit.
The safe operation of an electrosurgical pencil is vital not only to the patient, but also to the surgeon responsible for the patient's wellbeing and survival. Unexpected injury by a high current to either the patient or the surgeon can pose grave consequences. Dangerous electrical circuits can be completed if moisture, such as the typical body fluids which abound during surgery, accidentally reach the interior of the electrosurgical pencil. Since the surgeon's fingers frequently come in contact with the patient as well as the switch of the electrosurgical pencil, it is especially important to prevent the entrance of moisture from fingers around the switch. Because the surgeon may wish to set aside the electrosurgical pencil from time to time during surgery, it is important that the switch be arranged to prevent accidental jamming of the switch in an "on" position when finger pressure is removed. It is also especially important to provide a switch structure which eliminates the possibility of connection of all three conductors at one time.
Thus, it is clear that there exists a need in the art for an electrosurgical pencil with a control switch structure which prevents the entrance of moisture into the pencil, avoids the possibility of jamming the switch to energize the scalpel electrode when finger pressure is removed from the switch, prevents stripping of the electrical contacts when the cable or cord is pulled, and eliminates the possibility of simultaneously connecting all three conductors by inadvertent finger pressure. Additionally, there exists the need for a low cost disposable electrosurgical pencil of greatly simplified internal construction, and an economical process for manufacturing same, which allows fast assembly with reliable, easily insertable operating components, labor cost reduction, and a sturdy construction suitable for use in a medical environment.